Knowledge of the basis upon which granivores select seeds is crucial to the understanding of granivory. In this study the preferences of three rodent granivores among seeds of 11 plants from the semi-arid Karoo of South Africa were estimated, and related to the physical and chemical attributes of the seeds. Seed weights and calorific, moisture, protein, polyphenol, ash, lipid and silica contents were estimated and cell contents, soluble ash and soluble carbohydrate contents were derived from these values. These attributes were determined for both the intact seeds and the portion of the seed that is ingested by the mice. The efficiency with which mice ingested the seeds (in terms of time and mass) was recorded. All three mouse species ranked the seeds similarly, and the two species for which handling efficiency was measured did not differ in this regard. Preference hierachies were highly correlated with the rate of energy intake, as predicted by optimal foraging theory. There was no correlation between rodent preferences and the gross energy content of the seeds, emphasising the importance of measuring relevant parameters. The energy yield of the seeds calculated here, in conjunction with rodent population energy requirements and dietary data, may be used to estimate potential granivore impact on the seed production of the plant community.

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The feeding habits of black rhinoceros were studied in the Addo Elephant National Park, Republic of South Africa, using the "feeding track" method and recording bites taken. A total sample of 59 feeding tracks, 5 540 plants and 17 191 bites were recorded from June 1976 to March 1977. The rhino fed largely on woody shrubs but also took forbs, grass and succulent plants. During dry periods the rhino were selecting succulent plants with a high moisture content rather than woody plants. A total of 111 plant species were utilized. During dry months the feeding rate was greater than wet months. Physical analysis of faeces composition confirmed conclusions drawn from observations. Chemical analyses of faeces indicated that mean crude protein values varied with rainfall and herbage quality, ash values were strongly influenced by the intake of plant roots and dust during dry periods, acid detergent fibre was highest during unfavourable periods and low during favourable periods.

Upogebia africana were regularly and quantitatively sampled in the Swartkops estuary. At the site with 'stunted' prawns a well-defined spring (July to October) and summer (December to March) breeding cycle was recorded. The 'stunted' female prawns produced two broods of eggs per annum and the brood size ranged from about 305 to 2282 eggs depending on the size of the female. At the site with large prawns the spring and summer breeding cycles tended to merge, forming a longer breeding season, with the adult females apparently producing three broods of eggs per annum. The brood size of these females ranged from about 1304 to 4819 eggs. The calculated reproductive output (Pr) and reproductive biomass ratio (Pr/B) of the latter population were much greater than those of the 'stunted' prawns (1331 kJ m-2 y-1 and 0,53 v. 332 kJ m-2 y-1 and 0,26). Bevolkings van normale en 'verpotte' (volwasse karapakslengtes = 17,0-24,0 en 12,0-19,0 mm respektiewelik) Upogebia africana in die Swartkopsgetyrivier is met gereelde tussenposes kwantitatief gemonster. By die monsternemingspunt met die 'verpotte' garnale is goed gedefinieerde lente-(Julie tot Oktober) en somer-(Desember tot Maart) broeisiklusse waargeneem. Die 'verpotte' wyfiegarnale produseer twee broeisels per jaar en die grootte van die broeisel varieer van ongeveer 305 tot 2282 eiers afhangende van die grootte van die wyfie. By die monsternemingspunt met normale grootte garnale het die lente-en somer-broeisiklusse oorvleuel om 'n langer broeitydperk te vorm en die wyfies het blykbaar drie broeisels per jaar geproduseer. Die broeiselgrootte van hierdie wyfies varieer van ongeveer 1304 tot 4819 eiers. Die berekende reproduktiewe produksie (Pr) en die reproduktiewe biomassa-verhouding (Pr/B) van die laasgenoemde bevolking is baie groter as die van die 'verpotte' garnale (1331 kJ m-2 r 1 en 0,53 v. 332 kJ m-2 r 1 en 0,26).